The ressourcement (return to sources) is often named as the more conservative movement in 20th C. theology, especially at and after Vatican II, it's opposite number being aggiornamento (updating, adapting "to today"). I'm not sure what "conservative" means here. Though this book may teach me otherwise, my impression to date is that ressourcement was a revolutionary movement, a return that involved jumping over the heritage that was actually handed down in favor of an historical reconstruction.
Something tells me my reading of Nicolás Gómez Dávila (the Colombian philosopher) will be helpful in dealing with ressourcement and "historical" theology. History is a young discipline, and theologians are in love with it -- perhaps as they were once in love with philosophy? Gómez Dávila warns always against solutions and reforms: it is not he, the reactionary, who thinks a return to the past will solve things; instead the reactionary seeks shade from current madness, is skeptical but not hopeless, and waits on divine deliverance while he lives and works against fraud, intellectual dishonesty, and barbarism.
I like NGD more and more.